1. Field of the Invention
The present invention relates to a unit for beading tires usable, in particular, in tire changing machines or the like.
2. Description of the Related Art
As is known, so-called “tire changing” machines are commonly used inside workshops to remove and fit motor-vehicle wheel tires.
Such tire changing machines generally comprise a frame suitable for supporting a grip and start of rotation part of the rim of a wheel on/from which a tire has to be fitted/removed, and one or more tools for fitting and removing the tire itself It is also known that, before being able to completely remove a tire from the rim, the two beads have to be detached from the respective bead retainer edges positioned along the perimeter of the rim and which delimit the housing seat of the tire itself.
This operation is performed by means of a special beading unit, normally fitted to the tire changing machine itself.
This beading unit commonly comprises a horizontal arm, supported sliding vertically, at one extremity, by a bearing structure associated with the frame of the tire changing machine and having, at the opposite extremity, a special beading tool, of the type of a beading disc or the like.
In particular, the bearing structure commonly comprises a supporting upright associated with the frame of the tire changing machine and a carriage sliding along such upright and suitable for supporting the horizontal arm with the beading disc.
In a first known solution, the horizontal arm is of the telescopic type and can be extended or retracted longitudinally by means of the operation of one or more actuators, so as to allow the movement of the beading disc along a rectilinear direction and towards the rotation axis of the wheel, for the correct positioning of the beading tool on one side of the tire to be beaded, in proximity of one of the edges of the rim.
In point of fact, during use, the horizontal arm is positioned above the wheel, arranged horizontally and anchored to the grip part of the tire changing machine, and is extended or retracted until it reaches the correct positioning of the beading disc on one side of the tire to be beaded, in proximity of one of the edges of the rim.
Subsequently, the sliding carriage is moved downwards and, consequently, the beading disc presses on the tire and causes the detachment of a section of the bead from the rim edge.
To allow a correct detachment of such section of the bead from the rim, the further forward movement is known, after the lowering of the arm, of the beading disc along a rectilinear direction and towards the rotation axis of the wheel.
Such further forward movement of the roller is made through an additional extension of the telescopic element making up the horizontal arm, operated by a further actuator.
In particular, the further forward movement of the beading disc, together with the rotation of the wheel by means of the grip part, allow the detachment of the tire bead along the entire perimeter of the rim edge.
In a second known solution, the beading unit comprises a horizontal arm composed of a rod of predefined length fastened to the sliding carriage along the bearing structure.
The movement of the beading disc along a rectilinear direction, towards and away from the rotation axis of the wheel, is given by the movement of the bearing structure itself.
In point of fact, such bearing structure is fitted sliding along a rectilinear guide and is moved by operation of actuator means.
In this case, the further forward movement of the beading disc for the correct and complete detachment of the section of bead from the relative edge is carried out by means of a further movement of the bearing structure along the above-mentioned rectilinear direction, operated by a further actuator.
The known beading units described above are not, however, without drawbacks. In particular, the further forward movement of the beading tool towards the rim occurs along a rectilinear direction substantially at right angles to the tangential direction of rotation of the wheel on the grip part of the tire changing machine. This produces structural stresses on the tire that are not negligible and which are caused by the pressure of the tool itself and which, in some cases, can cause damage to the tire.
Furthermore, the beading tool must be moved by means of actuators with enough power to overcome the resistance opposed by the tire.
Consequently, the need to use high-power actuators affects in a far from negligible way the final cost of the beading unit.